How do i rotate set of models that make a bigger model(a car) to 0°?
If you select several objects and begin a rotation using the r key they will rotate as a unit, preserving relative position and orientation (unless pivoting around Individual Origins).

If the pivot point that blender picks (default is median) is not to your liking, you can change the pivot point to something like Cursor or maybe Active Element.  The 3D Cursor can be set to any coordinate using the n sidebar.